Noncooperative Multimode Precoding with Limited Feedback in MIMO Interference Channels

In a K-user N×N MIMO interference channel, each user achieves N/2 degrees of freedom through the concept of interference alignment [1], which utilizes the reciprocity of wireless channels. In nonreciprocal MIMO interference channels, [1] needs huge feedback overhead since each receiver should inform each transmitter how much interference it induces. When the bandwidth of the feedback channel is limited, we can employ the concept of limited feedback. We may also allow each user to determine the number of transmitted data streams adaptively according to the given channel condition. In a single-user MIMO system, this concept has been referred to as multimode precoding [2]. In this work, we consider a nonreciprocal MIMO interference channel where multiple transmitter-receiver pairs exist and propose an iterative multimode precoding scheme where each pair iteratively updates the number of transmitted data streams and the corresponding precoder without cooperation. It is also found that the iterative multimode [ ] [ ] [ ] [ ] [ ] [ ] [ ] [ ] = , k kk k k kl l l k